Results 51 to 60 of about 1,774 (127)

First Global Machine Learning Model to Predict the Rate of TEC Index (ROTI) Response to X‐Class Solar Flares

Space Weather, Volume 23, Issue 3, March 2025.
Abstract Solar flares are bursts of electromagnetic radiation originating in the Sun's atmosphere. Solar flares cause a rapid increase in ionization in the ionosphere, resulting in radio signal interference. This paper aims to predict the ionospheric response to the solar flare of various characteristics in all latitudes around the dayside ionosphere ...
A. Mahmoudian, F. Ghorbali, M. Vazifehkhah Hafteh   +2 more
wiley   +1 more source

First Observations of a Geomagnetic Superstorm With a Sub‐L1 Monitor

Space Weather, Volume 23, Issue 3, March 2025.
Abstract Forecasting the geomagnetic effects of solar coronal mass ejections (CMEs) is currently an unsolved problem. CMEs, responsible for the largest values of the north‐south component of the interplanetary magnetic field, are the key driver of intense and extreme geomagnetic activity.
E. Weiler, C. Möstl, E. E. Davies, A. M. Veronig, U. V. Amerstorfer, T. Amerstorfer, J. Le Louëdec, M. Bauer, N. Lugaz, V. Haberle, H. T. Rüdisser, S. Majumdar, M. Reiss   +12 more
wiley   +1 more source

A New Version of Reimers' law of Mass Loss Based on a Physical Approach [PDF]

, 2005
We present a new semi-empirical relation for the mass loss of cool stellar winds, which so far has frequently been described by "Reimers' law".
Bohn H. U., Boynton G. C., de Jager C., Fusi-Pecci F., K.-P. Schröder, M. Cuntz, Nieuwenhuijzen H., Reimers D., Reimers D., Ulmschneider P.   +9 more
core   +1 more source

Decent Estimate of CME Arrival Time From a Data‐Assimilated Ensemble in the Alfvén Wave Solar Atmosphere Model (DECADE‐AWSoM)

Space Weather, Volume 23, Issue 1, January 2025.
Abstract Forecasting the arrival time of Earth‐directed coronal mass ejections (CMEs) via physics‐based simulations is an essential but challenging task in space weather research due to the complexity of the underlying physics and limited remote and in situ observations of these events. Data assimilation techniques can assist in constraining free model
Hongfan Chen, Nishtha Sachdeva, Zhenguang Huang, Bart van der Holst, Ward Manchester IV, Aniket Jivani, Shasha Zou, Yang Chen, Xun Huan, Gabor Toth   +9 more
wiley   +1 more source

Studies of the local interstellar medium [PDF]

The existing ultraviolet and optical data concerning late-type stars are discussed along with the acquisition and reduction of additional ultraviolet and simultaneous ground-based observation.
Dupree, A. K.
core   +1 more source

PHOENIX model chromospheres of mid- to late-type M dwarfs

, 2005
We present semi-empirical model chromospheres computed with the atmosphere code PHOENIX. The models are designed to fit the observed spectra of five mid- to late-type M dwarfs. Next to hydrogen lines from the Balmer series we used various metal lines, e.
Andretta, Ayres, Ayres, B. Fuhrmeister, Barklem, Carlsson, Cram, Dahn, Delfosse, Falchi, Fuhrmeister, Fuhrmeister, Gizis, Hall, Hanuschik, Hauschildt, Hawley, J. H. M. M. Schmitt, Jevremovic, Johns-Krull, Jones, Jordan, Leggett, Liebert, Mauas, Mauas, Mauas, Mohanty, Mould, P. H. Hauschildt, Saar, Short, Short, Short, Vernazza, Wedemeyer, Young   +36 more
core   +1 more source

High-pressure transition regions in stellar model chromospheres

The Astrophysical Journal, 1979
The implications of recent ultraviolet observations of stellar transition-region lines for calculations of the Ca II and Mg II resonance lines are investigated. It is found that the adoption of high transition-region pressures for stars with active chromospheres, such as Lambda And and Alpha Aur, can be consistent with observed Ca II fluxes, contrary ...
S. L. Baliunas, E. H. Avrett, L. Hartmann, A. K. Dupree   +3 more
openaire   +1 more source

Chromospheric and Coronal Indicators of Stellar Magnetic Structure [PDF]

Symposium - International Astronomical Union, 1983
This paper discusses attempts to derive information on magnetic structure in late-type stars, only from emission fluxes in the cores of the Ca II H and K lines, in UV emission lines and in soft X-rays — and from relations between these emission fluxes. However simpleminded and indirect this approach may seem, it brings out stimulating results.
openaire   +1 more source

An IUE's eye view of cool-star outer atmospheres [PDF]

Three topics are discussed which together demonstrate the power of the IUE to probe the occurrences of chromospheres and coronas in the cool half of the HR diagram.
Ayres, T. R.
core   +1 more source

Evidence for extended chromospheres surrounding red giant stars [PDF]

Observational evidence and theoretical arguments are summarized which indicate that regions of partially ionized hydrogen extending several stellar radii are an important feature of red giant and supergiant stars.
Stencel, R. E.
core   +1 more source